The chancellor, Gordon Brown, last night doused hopes of early UK entry into the euro when he insisted that deep-seated Treasury doubts about the economics of monetary union would have to be overcome before Tony Blair could contemplate a referendum on the single currency.

In a speech seen as an attempt to counter the impression left by Mr Blair's address to the Labour party conference that an early plebiscite would be held by spring 2003, the chancellor said he would not "fudge or short-cut" the assessment.

Mr Brown told the CBI in Birmingham that the Treasury, which has grown increasingly concerned about the weakness of the euro and the performance of the European Central Bank since the single currency's launch in 1999, would take a "rigorous and comprehensive" look at the five tests, based on extensive technical and preliminary work.

Sources said Mr Brown wanted to dispel the idea that the prime minister's speech a month ago meant the political decision to join the single currency had already been taken and meeting the five tests would be simply a rubber-stamping exercise.

Although the chancellor reiterated his support for the euro in principle, his speech made it clear there may be no referendum in this parliament.

Mr Blair, while noting in Brighton that the five tests were more than window dressing, had increased speculation that the government was committed to entry when he told the party conference he would hold a referendum in this parliament if the economic conditions were right.

Mr Brown's speech last night fleshed out the details of the preliminary work on the tests, outlining a number of serious hurdles that will have to be overcome before the Treasury would recommend entry.

With Britain growing faster and enjoying lower unemployment than the other leading economies in Europe, the chancellor said he wanted to assess whether the UK economy could be permanently brought into line with the eurozone.

"It is not just in Britain but in Europe as a whole that a modern route to both economic stability and a more entrepreneurial economy based on economic reform is needed," the chancellor said.

He stressed that Treasury officials would investigate whether Europe's labour, product and capital markets are as flexible as those in Britain, test whether the exchange rate would remain stable when adjusted for inflation, and investigate the impact of the single currency on three areas where the UK has been strong in recent years - job creation, financial services and attracting inward investment.

"Because the government is determined that we will make the right long-term decisions for Britain, we will not take risks with Britain's long-term stability," Mr Brown said.

"So the assessment as to whether it is in the British national economic interest or not will be comprehensive and rigorous. It is only on this basis - taking into account all relevant economic information - that the cabinet will decide whether to recommend membership to parliament and then to the British people."

The chancellor expressed concerns that only half the economic gains promised from the creation of the single market had been achieved, stressing the need for further economic reform in Europe.

Mr Brown's comments came as an ICM poll of 1,000 people carried out for the anti-euro no campaign showed the events of September 11 may have turned some voters against the euro.

Asked whether they thought the threat of terrorist attacks made it more important that Britain "join the euro and integrate further with the rest of Europe," or "keep the pound and keep control of our own affairs," more than twice as many thought staying out of the euro was the right response to the terror attacks.